A device that receives electrical power from a power source, such as an electrical grid, a battery, or an electric generator, can include a power factor correction (PFC) circuit. Devices that are capable of power factor correction can increase the efficiency of the power source by making the load “seen” by the power source appear more resistive, rather than capacitive or inductive, thus reducing the reactive power. The power factor of a load is based on the instantaneous voltage and the instantaneous current. For a power factor of one, the phase lag between the alternating input voltage and the corresponding alternating input current is zero.
A PFC circuit can be coupled to the input of another power converter (e.g., a flyback converter) and to the output of a rectifier. The PFC circuit and the other power converter together may form a switch mode power supply (SNIPS). The PFC circuit may include a flyback converter topology or a boost converter topology. To increase the power factor, a controller may control the switching operation of the PFC circuit such that the input current more closely follows the input voltage to reduce the phase lag between the input voltage and the input current. The controller may use quasi-resonant switching for the PFC circuit, where the switching frequency is not defined by a clock. The switching frequency range may vary depending on the input voltage and the electrical load.